Aluminium Die Casting Explained: Process, Benefits, Design Tips and Finishing Options

Cold chamber vs hot chamber

(and why aluminium is commonly cold chamber)

For aluminium, the process is typically cold chamber: the molten metal is held in a separate furnace/pot and then transferred into the shot chamber before injection. This approach is commonly used because aluminium processing temperatures are higher and can damage systems used in hot-chamber machines. 

While tooling and machine configuration vary by part, the core cycle is consistent:

• Die preparation – the die halves are cleaned, lubricated, and brought to operating conditions
• Injection – molten aluminium is injected under high pressure into the die cavity
• Solidification – the metal cools quickly inside the die
• Ejection – the die opens, and ejector systems release the casting
• Trimming & secondary operations – removal of gates/flash; then machining/finishing as required   

Across the industry, aluminium die casting is selected because it balances complexity, speed and repeatability.

Key benefits (in plain terms)

• Complex geometries with tight tolerances that can be difficult to achieve economically with machining alone
• Smooth or textured surface finishes often reduce secondary work
• High-volume production capability, with rapid cycle times suited to repeat runs
• Lightweight, good strength-to-weight performance, and good conductivity characteristics (thermal/electrical)
• Recyclability, supporting circularity objectives in materials management 

Aluminium die casting is widely used where organisations require large quantities of consistent parts and where weight, surface finish, and functional performance are essential. 

Common application patterns include:

• Housings and enclosures
• Brackets, mounts, and structural nodes
• Components requiring machined interfaces (e.g., sealing faces, bores, threaded holes) after casting

A common mistake is treating die casting as “send CAD, receive parts.” In practice, a few early design decisions strongly influence tool complexity, defect risk and downstream machining.

1) Parting line planning

Because the die separates into halves, you need an intentional plan for where that split occurs (the parting line). It affects aesthetics, flash risk, and the feasibility of ejecting the part cleanly.

2) Injection strategy and fill behaviour

Injection points (and, where applicable, multiple gates) are used so the molten metal fills the cavity before it starts to freeze—particularly important for thin sections or highly detailed features. 

3) Wall thickness and consistency

Modern capability can support thin walls, but consistency is often a practical goal because it supports predictable fill and cooling behaviour and reduces distortion. 

4) Draft angles, ribs, and “castability”

Draft supports release from the die, while ribbing can add stiffness without adding excessive mass. Tooling guidance (draft/ribs/parting lines) should be considered early—especially if the part will later be machined in critical areas. 

Die-cast parts often require minimal machining, but most engineering-grade components still need some post-cast operations to hit critical tolerances and functional interfaces.

Common secondary operations

• Drilling, tapping, thread forming and critical surface machining
• Surface refinement to address seams at the die split or cosmetic requirements (e.g., abrasive processes)
• Surface coatings, such as powder coating, for protective and aesthetic performance

Relevant internal links:

• Powder coating service: https://www.bwcprofiles.co.uk/powder-coating
• Finishing overview (powder coating, anodising, etc.): https://www.bwcprofiles.co.uk/finishing
• Powder coating guide (Academy): https://www.bwcprofiles.co.uk/extrusion-academy/your-guide-to-powder-coating

Supplier changeovers are a common reason projects stall—particularly when tooling, qualification, and secondary operations are spread across multiple vendors.

BWC Profiles explicitly supports tool conversion/migration, with the aim of minimising disruption and re-qualifying tools quickly.
This is often most effective when machining, finishing, and assembly are integrated into the same delivery plan (fewer handoffs, fewer queues, clearer accountability).

Related internal link:

• Casting to completion (integrating die castings with extrusions): https://www.bwcprofiles.co.uk/extrusion-academy/from-casting-to-completion-integrating-aluminium-die-castings-with-extruded-components

BWC Profiles is a UK-based manufacturing group (established in 1999) providing end-to-end design and supply, including die castings, machining/finishing and assembly, alongside aluminium extrusion, sheet metal, plastics and logistics support.

Key die casting capability highlights include:

• High-pressure die casting (aluminium/aluminium alloys)
• Cold chamber process for aluminium 
• Machine capacity: 150–1650T 
• CNC machining & finishing (incl. 5-axis CNC, integrated inspection, powder coating)
• Assembly & integration (castings through to finished assemblies)

If you have a CAD model and target volumes, we can quickly advise on castability, tooling approach, machining/finishing needs, and what’s required to move from prototype intent to a stable production.